In obtaining well logging measurements, a logging tool carrying one or more exploring or measuring devices is lowered into a wellbore for measuring various characteristics of sub-surface earth formations. It is desirable in many instances to provide one or more visible records or logs of the investigated sub-surface characteristics at the well site within a relatively short time after the log has been run. Such logs may directly represent one or more analog type continuous measurements such as conductivity, spontaneous potential, sonic .DELTA.t, or gamma ray. Moreover, other logs may be representative of computed information which is derived by combining one or more of these direct measurements. Present well logging systems, are, of course, capable of providing suitable logs of such direct measurements or logs produced from relatively simple analog or special purpose digital computing equipment shortly after the completion of a well logging run. However, logs showing data which requires relatively complex processing and computation have heretofore been unavailable for many hours or even serveral days after the logging runs. These time delays have been alleviated substantially by the current practice of transmitting the well logging measurements to a distant computer center for processing and computation of the data. Nevertheless, even with such transmissions, there can still be situations where the resulting time delays are too long.
It also will be appreciated that many different types of well logs have been developed over the years for providing different information concerning various formation characteristics. Consequently, a great deal of complex downhole equipment, as well as the associated surface equipment, has been developed for each logging service. The complexity of much of this equipment has, of course, placed a substantial burden on the operating personnel to be certain that the logging tools are properly set up and calibrated and are being correctly controlled during logging.
Therefore, it is an object of this invention to provide a complete well logging system suitable for producing all types of high quality logs from wellbore data obtained from existing downhole logging tools.
It is a further object of this invention to provide a well logging system which requires a minimum amount of personnel interaction during a logging operation.